2016 ASHRAE Annual Conference

The purpose of this research was to investigate the ventilation requirements of an exhaust hood for multiple cooking appliances. There are two types of exhaust hoods in commercial kitchens: one is for a single cooking appliance, the other is for multiple cooking appliances. The face velocity of 60 fpm (0.3m/s) at the exhaust hoods opening is usually adopted as typical ventilation rate in Japanese commercial kitchen. Though the larger size of exhaust hoods opening increase the ventilation requirements, the amount of heat generation from cooking appliances under the exhaust hood is not reflected to the ventilation requirements. It seems to be necessary to know the ventilation requirements of exhaust hoods for multiple cooking appliances because the cooking appliances installed over multiple cooking appliances are various characteristics of heat generation. We investigated whether the sum of the ventilation requirements of exhaust hoods installed over each single cooking appliance is regarded as the ventilation requirements of exhaust hood for multiple cooking appliances. We measured capture efficiencies of exhaust hoods installed over single and multiple cooking appliances. Provided that the permissive level of capture efficiency is 90 percent, the ventilation rates of exhaust hoods for a fryer, noodle cooker, and IH table (single cooking appliance) were 253 cfm (430m³/h), 221 cfm (375m³/h), 194 cfm(330m³/h), respectively. The ventilation rates of exhaust hoods for a fryer with two IH tables and a noodle cooker with two IH tables (multiple cooking appliances) were 430 cfm (730m³/h) and 470 cfm (800m³/h), respectively. The sum of the ventilation rates of exhaust hoods for a fryer with IH tables and a noodle cooker with IH tables were 642 cfm (1090m³/h) and 610 cfm (1035m³/h), respectively. The sum of the ventilation rates for single cooking appliances is higher than that measured in the case of exhaust hoods for multiple cooking appliances. These results indicate that the capture and containment performance of exhaust hoods for multiple cooking appliances is higher than that of exhaust hoods for single cooking appliances. The size of exhaust hood’s opening for multiple cooking appliances is large compared with the exhaust hoods for single cooking appliances. Therefore it is easy for the exhaust hoods for multiple cooking appliances to capture thermal plumes even if thermal plumes are expanded by air disturbance. It suggests that the sum of the ventilation rates for single cooking appliances is the simplest way to estimate the ventilation rates for multiple cooking appliances.

The main goal of laboratory ventilation systems is to maintain certain levels of contaminant concentrations to provide safe environment for all personnel at all locations within the laboratory space. Laboratories frequently employ high ventilation rates with single pass outside air without any recirculation which makes laboratory ventilation systems energy intensive. The locations of supply and exhaust air play important role in determining the flow path of the supply air. Ideally the supply air should effectively sweep the laboratory space over the contaminant sources and dilute the contaminant levels without significant air recirculation. This paper with the help Computational Fluid Dynamics (CFD) analysis will evaluate the impact of various parameters on the effectiveness of contaminant removal. These parameters include the supply airflow rate, supply and exhaust locations, contaminant generation rates and locations of contaminant sources, and type of exhaust systems involving exposure control devices. Ventilation effectiveness will be evaluated by analyzing three dimensional distribution of contaminant concentration along with the three dimensional airflow patterns in the space. This analysis will provide valuable insights to practicing and design engineers related to the design and operation of laboratory ventilation systems.

Although full-field simulation using computational fluid dynamics and heat transfer (CFD/HT) tools can be applied to predict the flow and temperature fields inside data centers, their running time remains the biggest challenge to most modelers. From a simulation standpoint, there are still rooms for improving the speed of a full-field simulation process of a CFD/HT model whose bounded domain mostly consists of inviscid regions such as data center. Since the inviscid domain is mainly solved using Euler equations, the computing time for it is much faster than solving full Navier-Stokes equations with turbulent models for viscous domains. However, it is less desired to fully replace the viscous regions due its incapability of capturing the physics in these regions such as turbulence. Therefore, if inviscid domain is solved simultaneously with viscous domain, both the speed and accuracy will be much improved. In this paper, the inviscid-viscous coupling strategy is introduced in the solution domain to drastically reduce the running time while preserving the accuracy of a data center model. New criteria for dividing the inviscid, viscous regions, as well as interface region are presented. Step by step instruction on how to construct such regions for a data center model is also provided. The results show this approach’s superb simulation speed, while the accuracy is mostly retained from a full CFD/HT simulation.